/**
 * *****************************************************************************
 * Copyright 2011 See AUTHORS file.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 * ****************************************************************************
 */
package sg.atom.utils.datastructure.collection;


import sg.atom.utils._beta.functional.Predicate;
import sg.atom.utils._commons.ArrayReflection;
import java.util.Comparator;
import java.util.Iterator;
import java.util.NoSuchElementException;
import sg.atom.utils._beta.functional.PredicateIterable;
import sg.atom.utils.datastructure.collection.sort.Sorts;
import sg.atom.utils.math.AtomFastMath;

/**
 * A resizable, ordered or unordered array of objects. If unordered, this class
 * avoids a memory copy when removing elements (the last element is moved to the
 * removed element's position).
 *
 * @author Nathan Sweet
 */
public class Array<T> implements Iterable<T> {

    /**
     * Provides direct access to the underlying array. If the Array's generic
     * type is not Object, this field may only be accessed if the
     * {@link Array#Array(boolean, int, Class)} constructor was used.
     */
    public T[] items;
    public int size;
    public boolean ordered;
    private ArrayIterable iterable;
    private PredicateIterable<T> predicateIterable;

    /**
     * Creates an ordered array with a capacity of 16.
     */
    public Array() {
        this(true, 16);
    }

    /**
     * Creates an ordered array with the specified capacity.
     */
    public Array(int capacity) {
        this(true, capacity);
    }

    /**
     * @param ordered If false, methods that remove elements may change the
     * order of other elements in the array, which avoids a memory copy.
     * @param capacity Any elements added beyond this will cause the backing
     * array to be grown.
     */
    public Array(boolean ordered, int capacity) {
        this.ordered = ordered;
        items = (T[]) new Object[capacity];
    }

    /**
     * Creates a new array with {@link #items} of the specified type.
     *
     * @param ordered If false, methods that remove elements may change the
     * order of other elements in the array, which avoids a memory copy.
     * @param capacity Any elements added beyond this will cause the backing
     * array to be grown.
     */
    public Array(boolean ordered, int capacity, Class arrayType) {
        this.ordered = ordered;
        items = (T[]) ArrayReflection.newInstance(arrayType, capacity);
    }

    /**
     * Creates an ordered array with {@link #items} of the specified type and a
     * capacity of 16.
     */
    public Array(Class arrayType) {
        this(true, 16, arrayType);
    }

    /**
     * Creates a new array containing the elements in the specified array. The
     * new array will have the same type of backing array and will be ordered if
     * the specified array is ordered. The capacity is set to the number of
     * elements, so any subsequent elements added will cause the backing array
     * to be grown.
     */
    public Array(Array<? extends T> array) {
        this(array.ordered, array.size, array.items.getClass().getComponentType());
        size = array.size;
        System.arraycopy(array.items, 0, items, 0, size);
    }

    /**
     * Creates a new ordered array containing the elements in the specified
     * array. The new array will have the same type of backing array. The
     * capacity is set to the number of elements, so any subsequent elements
     * added will cause the backing array to be grown.
     */
    public Array(T[] array) {
        this(true, array, 0, array.length);
    }

    /**
     * Creates a new array containing the elements in the specified array. The
     * new array will have the same type of backing array. The capacity is set
     * to the number of elements, so any subsequent elements added will cause
     * the backing array to be grown.
     *
     * @param ordered If false, methods that remove elements may change the
     * order of other elements in the array, which avoids a memory copy.
     */
    public Array(boolean ordered, T[] array, int start, int count) {
        this(ordered, count, (Class) array.getClass().getComponentType());
        size = count;
        System.arraycopy(array, 0, items, 0, size);
    }

    public void add(T value) {
        T[] items = this.items;
        if (size == items.length) {
            items = resize(Math.max(8, (int) (size * 1.75f)));
        }
        items[size++] = value;
    }

    public void addAll(Array<? extends T> array) {
        addAll(array, 0, array.size);
    }

    public void addAll(Array<? extends T> array, int offset, int length) {
        if (offset + length > array.size) {
            throw new IllegalArgumentException("offset + length must be <= size: " + offset + " + " + length + " <= " + array.size);
        }
        addAll((T[]) array.items, offset, length);
    }

    public void addAll(T... array) {
        addAll(array, 0, array.length);
    }

    public void addAll(T[] array, int offset, int length) {
        T[] items = this.items;
        int sizeNeeded = size + length;
        if (sizeNeeded > items.length) {
            items = resize(Math.max(8, (int) (sizeNeeded * 1.75f)));
        }
        System.arraycopy(array, offset, items, size, length);
        size += length;
    }

    public T get(int index) {
        if (index >= size) {
            throw new IndexOutOfBoundsException("index can't be >= size: " + index + " >= " + size);
        }
        return items[index];
    }

    public void set(int index, T value) {
        if (index >= size) {
            throw new IndexOutOfBoundsException("index can't be >= size: " + index + " >= " + size);
        }
        items[index] = value;
    }

    public void insert(int index, T value) {
        if (index > size) {
            throw new IndexOutOfBoundsException("index can't be > size: " + index + " > " + size);
        }
        T[] items = this.items;
        if (size == items.length) {
            items = resize(Math.max(8, (int) (size * 1.75f)));
        }
        if (ordered) {
            System.arraycopy(items, index, items, index + 1, size - index);
        } else {
            items[size] = items[index];
        }
        size++;
        items[index] = value;
    }

    public void swap(int first, int second) {
        if (first >= size) {
            throw new IndexOutOfBoundsException("first can't be >= size: " + first + " >= " + size);
        }
        if (second >= size) {
            throw new IndexOutOfBoundsException("second can't be >= size: " + second + " >= " + size);
        }
        T[] items = this.items;
        T firstValue = items[first];
        items[first] = items[second];
        items[second] = firstValue;
    }

    /**
     * Returns if this array contains value.
     *
     * @param identity If true, == comparison will be used. If false, .equals()
     * comparison will be used.
     * @return true if array contains value, false if it doesn't
     */
    public boolean contains(T value, boolean identity) {
        T[] items = this.items;
        int i = size - 1;
        if (identity || value == null) {
            while (i >= 0) {
                if (items[i--] == value) {
                    return true;
                }
            }
        } else {
            while (i >= 0) {
                if (value.equals(items[i--])) {
                    return true;
                }
            }
        }
        return false;
    }

    /**
     * Returns an index of first occurrence of value in array or -1 if no such
     * value exists
     *
     * @param identity If true, == comparison will be used. If false, .equals()
     * comparison will be used.
     * @return An index of first occurrence of value in array or -1 if no such
     * value exists
     */
    public int indexOf(T value, boolean identity) {
        T[] items = this.items;
        if (identity || value == null) {
            for (int i = 0, n = size; i < n; i++) {
                if (items[i] == value) {
                    return i;
                }
            }
        } else {
            for (int i = 0, n = size; i < n; i++) {
                if (value.equals(items[i])) {
                    return i;
                }
            }
        }
        return -1;
    }

    /**
     * Returns an index of last occurrence of value in array or -1 if no such
     * value exists. Search is started from the end of an array.
     *
     * @param identity If true, == comparison will be used. If false, .equals()
     * comparison will be used.
     * @return An index of last occurrence of value in array or -1 if no such
     * value exists
     */
    public int lastIndexOf(T value, boolean identity) {
        T[] items = this.items;
        if (identity || value == null) {
            for (int i = size - 1; i >= 0; i--) {
                if (items[i] == value) {
                    return i;
                }
            }
        } else {
            for (int i = size - 1; i >= 0; i--) {
                if (value.equals(items[i])) {
                    return i;
                }
            }
        }
        return -1;
    }

    /**
     * Removes value from an array if it exists.
     *
     * @param identity If true, == comparison will be used. If false, .equals()
     * comparison will be used.
     * @return true if value was found and removed, false otherwise
     */
    public boolean removeValue(T value, boolean identity) {
        T[] items = this.items;
        if (identity || value == null) {
            for (int i = 0, n = size; i < n; i++) {
                if (items[i] == value) {
                    removeIndex(i);
                    return true;
                }
            }
        } else {
            for (int i = 0, n = size; i < n; i++) {
                if (value.equals(items[i])) {
                    removeIndex(i);
                    return true;
                }
            }
        }
        return false;
    }

    /**
     * Removes and returns the item at the specified index.
     */
    public T removeIndex(int index) {
        if (index >= size) {
            throw new IndexOutOfBoundsException("index can't be >= size: " + index + " >= " + size);
        }
        T[] items = this.items;
        T value = (T) items[index];
        size--;
        if (ordered) {
            System.arraycopy(items, index + 1, items, index, size - index);
        } else {
            items[index] = items[size];
        }
        items[size] = null;
        return value;
    }

    /**
     * Removes from this array all of elements contained in the specified array.
     *
     * @param identity True to use ==, false to use .equals().
     * @return true if this array was modified.
     */
    public boolean removeAll(Array<? extends T> array, boolean identity) {
        int size = this.size;
        int startSize = size;
        T[] items = this.items;
        if (identity) {
            for (int i = 0, n = array.size; i < n; i++) {
                T item = array.get(i);
                for (int ii = 0; ii < size; ii++) {
                    if (item == items[ii]) {
                        removeIndex(ii);
                        size--;
                        break;
                    }
                }
            }
        } else {
            for (int i = 0, n = array.size; i < n; i++) {
                T item = array.get(i);
                for (int ii = 0; ii < size; ii++) {
                    if (item.equals(items[ii])) {
                        removeIndex(ii);
                        size--;
                        break;
                    }
                }
            }
        }
        return size != startSize;
    }

    /**
     * Removes and returns the last item.
     */
    public T pop() {
        if (size == 0) {
            throw new IllegalStateException("Array is empty.");
        }
        --size;
        T item = items[size];
        items[size] = null;
        return item;
    }

    /**
     * Returns the last item.
     */
    public T peek() {
        if (size == 0) {
            throw new IllegalStateException("Array is empty.");
        }
        return items[size - 1];
    }

    /**
     * Returns the first item.
     */
    public T first() {
        if (size == 0) {
            throw new IllegalStateException("Array is empty.");
        }
        return items[0];
    }

    public void clear() {
        T[] items = this.items;
        for (int i = 0, n = size; i < n; i++) {
            items[i] = null;
        }
        size = 0;
    }

    /**
     * Reduces the size of the backing array to the size of the actual items.
     * This is useful to release memory when many items have been removed, or if
     * it is known that more items will not be added.
     */
    public void shrink() {
        if (items.length == size) {
            return;
        }
        resize(size);
    }

    /**
     * Increases the size of the backing array to acommodate the specified
     * number of additional items. Useful before adding many items to avoid
     * multiple backing array resizes.
     *
     * @return {@link #items}
     */
    public T[] ensureCapacity(int additionalCapacity) {
        int sizeNeeded = size + additionalCapacity;
        if (sizeNeeded > items.length) {
            resize(Math.max(8, sizeNeeded));
        }
        return items;
    }

    /**
     * Creates a new backing array with the specified size containing the
     * current items.
     */
    protected T[] resize(int newSize) {
        T[] items = this.items;
        T[] newItems = (T[]) ArrayReflection.newInstance(items.getClass().getComponentType(), newSize);
        System.arraycopy(items, 0, newItems, 0, Math.min(size, newItems.length));
        this.items = newItems;
        return newItems;
    }

    /**
     * Sorts this array. The array elements must implement {@link Comparable}.
     * This method is not thread safe (uses {@link Sort#instance()}).
     */
    public void sort() {
        Sorts.instance().sort(items, 0, size);
    }

    /**
     * Sorts the array. This method is not thread safe (uses
     * {@link Sort#instance()}).
     */
    public void sort(Comparator<T> comparator) {
        Sorts.instance().sort(items, comparator, 0, size);
    }

    /**
     * Selects the nth-lowest element from the Array according to Comparator
     * ranking. This might partially sort the Array. The array must have a size
     * greater than 0, or a {@link sg.atom.utils.collection.GdxRuntimeException}
     * will be thrown.
     *
     * @see Select
     * @param comparator used for comparison
     * @param kthLowest rank of desired object according to comparison, n is
     * based on ordinal numbers, not array indices. for min value use 1, for max
     * value use size of array, using 0 results in runtime exception.
     * @return the value of the Nth lowest ranked object.
     */
    public T selectRanked(Comparator<T> comparator, int kthLowest) {
        if (kthLowest < 1) {
            throw new RuntimeException("nth_lowest must be greater than 0, 1 = first, 2 = second...");
        }
        return Select.instance().select(items, comparator, kthLowest, size);
    }

    /**
     * @see Array#selectRanked(java.util.Comparator, int)
     * @param comparator used for comparison
     * @param kthLowest rank of desired object according to comparison, n is
     * based on ordinal numbers, not array indices. for min value use 1, for max
     * value use size of array, using 0 results in runtime exception.
     * @return the index of the Nth lowest ranked object.
     */
    public int selectRankedIndex(Comparator<T> comparator, int kthLowest) {
        if (kthLowest < 1) {
            throw new RuntimeException("nth_lowest must be greater than 0, 1 = first, 2 = second...");
        }
        return Select.instance().selectIndex(items, comparator, kthLowest, size);
    }

    public void reverse() {
        T[] items = this.items;
        for (int i = 0, lastIndex = size - 1, n = size / 2; i < n; i++) {
            int ii = lastIndex - i;
            T temp = items[i];
            items[i] = items[ii];
            items[ii] = temp;
        }
    }

    public void shuffle() {
        T[] items = this.items;
        for (int i = size - 1; i >= 0; i--) {
            int ii = AtomFastMath.random(i);
            T temp = items[i];
            items[i] = items[ii];
            items[ii] = temp;
        }
    }

    /**
     * Returns an iterator for the items in the array. Remove is supported. Note
     * that the same iterator instance is returned each time this method is
     * called. Use the {@link ArrayIterator} constructor for nested or
     * multithreaded iteration.
     */
    public Iterator<T> iterator() {
        if (iterable == null) {
            iterable = new ArrayIterable(this);
        }
        return iterable.iterator();
    }

    /**
     * Returns an iterable for the selected items in the array. Remove is
     * supported, but not between hasNext() and next(). Note that the same
     * iterable instance is returned each time this method is called. Use the
     * {@link Predicate.PredicateIterable} constructor for nested or
     * multithreaded iteration.
     */
    public Iterable<T> select(Predicate<T> predicate) {
        if (predicateIterable == null) {
            predicateIterable = new PredicateIterable<T>(this, predicate);
        } else {
            predicateIterable.set(this, predicate);
        }
        return predicateIterable;
    }

    /**
     * Reduces the size of the array to the specified size. If the array is
     * already smaller than the specified size, no action is taken.
     */
    public void truncate(int newSize) {
        if (size <= newSize) {
            return;
        }
        for (int i = newSize; i < size; i++) {
            items[i] = null;
        }
        size = newSize;
    }

    /**
     * Returns a random item from the array, or null if the array is empty.
     */
    public T random() {
        if (size == 0) {
            return null;
        }
        return items[AtomFastMath.random(0, size - 1)];
    }

    /**
     * Returns the items as an array. Note the array is typed, so the
     * {@link #Array(Class)} constructor must have been used. Otherwise use
     * {@link #toArray(Class)} to specify the array type.
     */
    public T[] toArray() {
        return (T[]) toArray(items.getClass().getComponentType());
    }

    public <V> V[] toArray(Class type) {
        V[] result = (V[]) ArrayReflection.newInstance(type, size);
        System.arraycopy(items, 0, result, 0, size);
        return result;
    }

    public boolean equals(Object object) {
        if (object == this) {
            return true;
        }
        if (!(object instanceof Array)) {
            return false;
        }
        Array array = (Array) object;
        int n = size;
        if (n != array.size) {
            return false;
        }
        Object[] items1 = this.items;
        Object[] items2 = array.items;
        for (int i = 0; i < n; i++) {
            Object o1 = items1[i];
            Object o2 = items2[i];
            if (!(o1 == null ? o2 == null : o1.equals(o2))) {
                return false;
            }
        }
        return true;
    }

    public String toString() {
        if (size == 0) {
            return "[]";
        }
        T[] items = this.items;
        StringBuilder buffer = new StringBuilder(32);
        buffer.append('[');
        buffer.append(items[0]);
        for (int i = 1; i < size; i++) {
            buffer.append(", ");
            buffer.append(items[i]);
        }
        buffer.append(']');
        return buffer.toString();
    }

    public String toString(String separator) {
        if (size == 0) {
            return "";
        }
        T[] items = this.items;
        StringBuilder buffer = new StringBuilder(32);
        buffer.append(items[0]);
        for (int i = 1; i < size; i++) {
            buffer.append(separator);
            buffer.append(items[i]);
        }
        return buffer.toString();
    }

    static public class ArrayIterator<T> implements Iterator<T>, Iterable<T> {

        private final Array<T> array;
        private final boolean allowRemove;
        int index;
        boolean valid = true;

        public ArrayIterator(Array<T> array) {
            this(array, true);
        }

        public ArrayIterator(Array<T> array, boolean allowRemove) {
            this.array = array;
            this.allowRemove = allowRemove;
        }

        public boolean hasNext() {
            if (!valid) {
                throw new RuntimeException("#iterator() cannot be used nested.");
            }
            return index < array.size;
        }

        public T next() {
            if (index >= array.size) {
                throw new NoSuchElementException(String.valueOf(index));
            }
            if (!valid) {
                throw new RuntimeException("#iterator() cannot be used nested.");
            }
            return array.items[index++];
        }

        public void remove() {
            if (!allowRemove) {
                throw new RuntimeException("Remove not allowed.");
            }
            index--;
            array.removeIndex(index);
        }

        public void reset() {
            index = 0;
        }

        public Iterator<T> iterator() {
            return this;
        }
    }

    static public class ArrayIterable<T> implements Iterable<T> {

        private final Array<T> array;
        private final boolean allowRemove;
        private ArrayIterator iterator1, iterator2;

        public ArrayIterable(Array<T> array) {
            this(array, true);
        }

        public ArrayIterable(Array<T> array, boolean allowRemove) {
            this.array = array;
            this.allowRemove = allowRemove;
        }

        public Iterator<T> iterator() {
            if (iterator1 == null) {
                iterator1 = new ArrayIterator(array, allowRemove);
                iterator2 = new ArrayIterator(array, allowRemove);
            }
            if (!iterator1.valid) {
                iterator1.index = 0;
                iterator1.valid = true;
                iterator2.valid = false;
                return iterator1;
            }
            iterator2.index = 0;
            iterator2.valid = true;
            iterator1.valid = false;
            return iterator2;
        }
    }
}
